Could any one tell me what might be causing this issue?Thanks.
Looks like some belt slippage, or loose v-wheel. Also check that you pulleys are tight, the grub screw like to back out from time to time.
And that your POTs are tuned to the right setting. (Potentiometers)
Check out these threads for a troubleshooting guide and videos to make adjustments to various parts:
Thanks for all the help, tightened up all the belts and checked the v wheels and it seems to have helped a lot.
Don't think it's spot on yet but getting closer.
Thanks once again.